For reference in case if someone wants to backup/transfer the wallet files manually,
the wallet files were stored inside the android phone's
internal system data folder,
not in the internal storage (
root access is required)
Found this by using google search:
I just downloaded the electrum wallet on android. And since my smartphone is rooted then I tried to google also but never see an answer on it. So I tried to navigate it on my own and found it on
/data/data/org.electrum.electrum/files/data/wallets then there's "default_wallet" file there. So you need to have a jailbreak/rooted phone to navigate it.